1. Field of the Invention
The present invention relates to a head lamp device mounted on a vehicle, and particularly to a head lamp device which can be fixed with a bulb by using a bayonet mechanism in its installation.
2. Background Art
FIGS. 3 and 4 illustrate a construction of this type of a conventional head lamp device 90 employing, for example, a bulb 10 having three bayonet pawls 11. The head lamp device 90 has a bayonet holder 92 which consists of a base 92a, a cover 92b and other parts, has a shape to be engaged with the bayonet pawls 11 of the bulb 10, and provided at suitable position of such as a reflector 91 back face.
When the bulb 10 is installed in the head lamp device 90, the bulb 10 is inserted into the bayonet holder 92 at an inserted position IN wherein the bayonet pawls 11 thereof can be directly inserted. Subsequently, the bulb 10 is rotated clockwise to a fixed position FX, so that the bayonet pawls 11 can be fixed and held between the base 92a and the cover 92b.
After the bulb 10 has been fixed with the head lamp device 90 as described above, a feeder connector 20 provided on the vehicle body side is fixed with a socket 12 of the bulb 10 to connect the bulb 10 to a power supply of the vehicle and the bulb 10 can be turned on/off on demand.
Moreover, for the removal of the bulb 10, the bulb 10 rotates counterclockwise from the fixed position FX to the inserted position IN and then become removable because the bayonet pawls are released from the cover 92b. The bulb 10 is detachable in this simple way, so that an operator or a driver can easily replace a broken bulb with new one.
However, in the conventional head lamp device 90 as described above, the bulb 10 may be insufficiently rotated from the inserted position IN to the fixed position FX over the range of about 30.degree. to 40.degree. in the installation because inexperienced users for the replacement mostly operate the bulb.
For obtaining a specific light distribution in a head lamp bulb 10 having a main beam filament and a low beam filament, the fixed position FX of the bulb 10 in the head lamp device should be exactly specified so that the relationship between the bulb and the fixed position is appropriate.
For insufficient rotation as describe above, the specified light distribution may not be obtained. When the vehicle travels in the above status, it causes problems such as, for example dazzling to oncoming cars. For the insufficient rotation status of the bulb, another problem occurs such as, for coming off the bulb by a vibration of a driven vehicle as a result of an insufficient holding force to the bulb 10 within the bayonet holder 92. Therefore, such a head lamp device is desired to improve these problems.